1. Technical Field
The present disclosure relates to a proton conductor.
2. Description of the Related Art
A BaZrO3-based proton conductor has a high proton conductivity in a steam atmosphere and is expected to be applied to, for example, an electrolyte of a solid oxide fuel cell or the like.
A solid electrolyte containing a BaZrO3-based proton conductor has been known that the electrical conductivity of a crystal grain boundary of a polycrystalline substance is lower than that in crystal grains of the polycrystalline substance. Hence, for example, when a solid electrolyte containing a BaZrO3-based proton conductor is used as an electrolyte material of a solid oxide fuel cell, there has been a problem in that the entire resistance of the solid electrolyte is increased.
Japanese Unexamined Patent Application Publication No. 2009-23883 has disclosed a proton conductor (BaZr1−x−yMaxMbyO3) in which Zr of BaZrO3 is substituted by elements Ma and Mb (the element Ma is at least one type of element selected from Y, Ho, Er, Tm, Yb, and Lu; the element Mb is at least one type of element selected from Sc, and In; and 0<x<1, 0<y<1, 0<x+y<1, and x/y≥1 hold). According to the composition described above, since the crystal grain size of the proton conductor is increased, the rate of the crystal grain boundary to the entire polycrystalline substance is decreased. That is, since the rate of the crystal grain boundary having a higher resistance than that in the crystal grains is decreased, a proton conductor having a low entire resistance can be obtained.